Levisoceras is an early Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 ellesmerocerid

Ellesmerocerida

The Ellesmerocerida is a order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.-Morphology:...

 cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

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Morphology

Levisoceras is a distinctive ellesmeroceratid that combines rapid expansion a strong endogastric curvature. The cross section is compressed with the height increasing more rapidly than the width. The siphuncle is ventral and expands much as the shell itself. In one specimen the height was found to be around four centimetres and the width 2.5 cm. The septa are approximately flat.

Taxonomic Relations

Some 14 or so species have been named. Those more gently expanding approach Dakeoceras

Dakeoceras

Dakeoceras is a simple cyrtoconic ellesmeroceratid genus, all known species of which come from the Lower Canadian of North America....

in form. There is also an apparent transition between Levisoceras and Burenoceras

Burenoceras

Burenoceras is a genus of small, even tiny, Gasconadian cyrtoconic ellesmeroceratids in which the phragmocone -the chambered portion- is shorter that the living chamber....

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